The present invention relates to novel aromatic ether ketone polyamine compounds useful as curatives for polyepoxide compositions and as monomeric starting materials for the preparation of useful intermediates and useful thermoplastic and highly heat resistant polymers. The present invention also relates to methods for preparing the polyamines, epoxy resin compositions, intermediates and polymeric materials.
Polyamines are known to react with a wide variety of reactive groups to form useful compounds and compositions. Amine groups react with isocyanate groups to form ureas useful as herbicides and fungicides as well as in coatings and film applications. Amines react with carboxylic acid groups to form amides useful as film and fiber formers as well as coatings and thermoplastic molding compositions. When reacted with carboxylic acid anhydrides, amines are useful for forming polyamides exhibiting high temperature resistance which are employed in heat shield and wire enamels applications. Polyamines also react with epoxide prepolymers to cure them by a polyaddition reaction to form tough, cross-linked resinous compositions having utility as encapsulants for electronic components, adhesives, coatings and the like.
When the epoxy resin compositions are filled and reinforced with, for example, glass or graphite fibers, reinforced epoxy resin composites are obtained having high strength to weight ratios. These reinforced composite materials have found extensive use in the aircraft and aerospace industries, and in other applications where strength, corrosion resistance and light weight are desirable. For instance, fiber resin matrix materials have replaced aluminum and other metals in primary and secondary structures of modern military and commerical aircraft. Sporting equipment such as tennis rackets and golf clubs have also adopted fiber resin materials successfully.
Epoxy resin compositions and fiber modifications are abundant. Since the advent of fiber resin matrix materials, much effort has been expended in improving their properties and characteristics, including the development of many different curing systems.
Amine and polyamine curing agents have received wide acceptance, but the toxicity, low solubility, high exotherm and variable curing rates associated with the most commonly used amines, such as m-phenylenediamine, 4,4'-diaminodiphenyl methane and 4,4'-diaminodiphenyl sulfone, has made further improvement desirable. In the case of aircraft structural applications, epoxy resins cured with available curing agents are either too brittle or do not have sufficient strength and stiffness under hot/wet conditions. It is disclosed in U.K. Patent 1,182,377, which is incorporated herein by reference, that certain aromatic polyamines having the formula: ##STR1## wherein R represents the radical formed after elimination of the hydroxyl group of a polyhydric aliphatic, cycloaliphatic or araliphatic alcohol, Ar represents an optionally substituted phenylene or naphthylene radical, R' represents hydrogen or an alkyl radical an n represents an integer from 2 to 10, are effective as curing agents for a variety of polyepoxides, and the resulting cured compositions are useful as films, moldings, coatings and glass-reinforced laminates. There is no indication in the properties presented in the U.K. Patent that the curing agents exemplified therein will produce the combination of toughness and strength under hot/wet conditions essential for use in the above-mentioned structural applications.
In U.S. Pat. No. 3,932,360, diamine cured polyurethane products are described, in which the diamines are of the formula, e.g., ##STR2## wherein n is an integer from 2 to 12. This '360 patent does not deal with curing compounds having more than one epoxide group per molecule.
In Gillham et al, Organic Coatings and Applied Polymer Science Proceedings, Vol. 46, p. 592-598, March-April, 1982, polyepoxides cured with diamines of the immediately preceding formula (n is 3), are described.
In Chemical Abstracts, 90:39660y, bis(aminophenoxy) compounds, such as 4,4'-bis(3-aminophenoxy) diphenylsulfone, are disclosed to be useful crosslinking agents for bisphenol-A- epichlorohydrin copolymer resins and provided improved heat distortion temperature and improved flexibility to that cured epoxy resin, as compared with a similar composition cured with a diaminodiphenylmethane crosslinking agent.
In Chemical Abstracts, 91:158766t, thermosetting resin laminates having good flexibility and machinability are disclosed which are, prepared by impregnating a glass textile with a thermocurable composition comprising an epoxy resin (ARALDITE.RTM. 8011, from Ciba-Geigy Corporation); a diamine of the formula: ##STR3## wherein Z.sup.1, Z.sup.2 and Z.sup.3 are O, S, SO.sub.2, CH.sub.2, CO, CO.sub.2 or C(CH.sub.3).sub.2 and 2-ethyl-4-methylimidazole; processing the impregnated fabric at 160.degree. C. to form a prepreg; laying up several layers of prepregs and fusing at 170.degree. C. and 90 kg/cm.sup.2 for 11/2 hours.
In copending application, Ser. No. 584,700, filed Feb. 29, 1984, now U.S. Pat. No. 4,645,803, it is disclosed that neat resins comprising an epoxidic prepolymer having more than one epoxide group per molecule and a polyamine curing agent are provided with improved toughness and hot/wet modulus if the polyamine curing agent employed is an aromatic ether sulfone polyamine or aromatic ether ketone polyamine polyamine compound having the formula: ##STR4## wherein R is selected from ##STR5## m=n; and m and n are integers of from 1 to 5. Reinforced composites such as prepregs and laminates comprising these curable compositions as the resin component are disclosed to have improved compression strength and short beam shear strength under dry, hot and hot/wet conditions.
It has now been discovered that novel polyamine compounds having a backbone containing from about 3 to about 8 aromatic rings interspaced by ether and ketone groups are useful as monomeric reactants for forming polymeric materials exhibiting improved impact resistance, solvent resistance and moisture resistance, as compared with simpler aromatic polyamines, aromatic ether-sulfone polyamines or simple ether ketone polyamines. When the novel aromatic ether-ketone diamines of the present invention are used as curing agents for epoxy resin compositions both neat resins and reinforced epoxy resin composites are obtained which exhibit excellent retention of physical properties under hot/wet conditions.